Not sure why anyone wants to spray fire extinguishant into an engine intake.
Most engine fires are the result of oil or fuel leaks on the external systems of the engine.
Spraying chemicals in the intake results in loads of smoke out of the exhaust with the fire keeping it all warm!!!!!!!
Few modern helicopters seem to have proper fire access doors to the engine compartment.
The only decent access seems to be around the exhaust pipes (not up them). Most airport fire trucks would not have a nozzle that would fit in this space.